Callers tried to interrupt Scott Pleasants as he gave his testimony via Skype during the George Zimmerman trial on July 3.

The Zimmerman trial: Halftime highlights

By James Novogrod, Tom Winter and Tracy Connor, NBC News

Editor's note: This report contains graphic images and language from the trial of George Zimmerman.

Combative cross-examinations, graphic crime-scene evidence, two mothers and one very strange knock-knock joke.

There have been some memorable moments in the trial of George Zimmerman, which hit the midway point Friday when the prosecution rested after two weeks of testimony.

Lawyers for Zimmerman -- who has pleaded not guilty to second-degree murder and says he shot 17-year-old Trayvon Martin in self-defense – began laying out their case late Friday and will continue on Monday.

Here’s a look back at some of the highlights so far in the legal drama that is playing out a Sanford, Fla., courtroom and being closely watched across the nation:

The joke: Defense lawyer Don West tried to break the ice with jurors during his opening statement with some humor: “Knock, knock. Who’s there? George Zimmerman. George Zimmerman who? All right, good, you’re on the jury.”

It went over like a lead balloon inside the courtroom and out, and after a lunch break, West apologized to jurors for the attempt at levity.

Gary W. Green pool via Getty Images

A photo of Trayvon Martin from the night of the shooting was introduced as evidence during George Zimmerman's trial on June 25.

The photos: On the second day of testimony, jurors were shown a series of photographs of Martin’s body on the grass at the Retreat at Twin Lakes complex.

One taken by a neighbor showed him face down in the darkness.

Others taken by a police technician showed him on his back and under a tarp.

There was also a closeup of the coin-sized chest wound.

Martin’s father left the courtroom when they were introduced.

The first responder: Police Sgt. Anthony Raimondo painstakingly detailed his efforts to save Martin’s life after he arrived at the scene and found him without a pulse.

“I breathed for him,” he testified, describing how he performed CPR without a protective mask.

He also asked bystanders for Vaseline and plastic wrap so he could try to seal the wound before it was clear the teen could not be revived.

The lead investigator: Officer Chris Serino was a prosecution witness but may have helped the defense when he described how Zimmerman, purposely tricked into thinking there was video of the clash, said he had been hoping someone taped it.

“He’s either telling the truth or he’s a pathological liar,” Serino said.

He then added under further questioning that he believed Zimmerman.

The jury was later instructed to ignore Serino’s comment.

He also said inconsistencies in Zimmerman’s story were insignificant, but thought he exaggerated how he was hit.

The friend: Rachel Jeantel’s testimony about her phone conversation with Martin in the last moments of his life was unquestionably captivating and stirred outside debate over whether she was dismissive and hostile or just young and unsophisticated.

Jurors strained to hear her, but when West asked whether Martin might have lied to her during the call, her feelings came across loud and clear.

“That’s real retarded, sir,” she said.

The 19-year-old stuck to her story that Martin told her he was being followed by a “creepy-ass cracker,” but the defense underscored lies she admitted she told before the trial.

The neighbor: John Good testified that when he went out to investigate a commotion the night of Feb. 26, 2012, he saw someone in dark clothing straddling someone with lighter skin in what he described to cops as a “ground and pound” position.

The defense, which contends that Martin rained down blows on Zimmerman, seized on the phrase, a mixed martial arts term.

Good, however, also said he only saw arms swinging and did not know if any blows connected.

At one point, prosecutor Bernie de la Rionda even used water bottles to illustrate the body positions.

The injury report: Prosecutors called one medical examiner, Dr. Valerie Rao, as an expert witness — not to talk about Martin’s injuries, but Zimmerman’s.

She testified that they were “so minor,” not life-threatening and consistent with a single head strike against concrete.

Under cross-examination, she agreed there could have been more than one blow, but the defense will put on its own expert to support its claim that Zimmerman’s head was repeatedly slammed on the pavement.

Jacob Langston / Pool via EPA file

Callers tried to interrupt Scott Pleasants as he gave his testimony via Skype during the George Zimmerman trial on July 3.

The pranksters: When Zimmerman’s former criminal justice professor testified Wednesday via Skype, the screen was bombarded with the pings and pop-ups of incoming call requests, apparently from jokers who saw the prosecutor’s ID displayed.

“There’s now a really good chance that we’re being toyed with,” defense lawyer Mark O’Mara said.

“Hang up the phone,” the judge ordered.

The professor, Scott Pleasants, then continued his testimony by speaker phone.

The moms: Both Martin’s and Zimmerman’s mothers were brought to the stand Friday for the same purpose, to testify about screams for help heard in the background of a 911 call that could help the jury decide who was the aggressor and who was being attacked.

“I heard my son screaming,” Sybrina Fulton, Martin’s mother, told the court during her brief appearance on the stand.

About eight hours later, the defense called Gladys Zimmerman as its first witness. Asked who was screaming, she told the jury: “My son, George.” Zimmerman has pled not guilty to a second-degree murder charge.

Editor’s note: George Zimmerman has sued NBC Universal for defamation. The company strongly denies the allegation.